unbuffered cmd subprocess

hbd

@@ -355,7 +355,7 @@ answer
     if DEBUG > 0:
         log(None, "DBG: cmd %s" % cmd)
     try:
-        p = Popen(cmd, shell=False, bufsize=1, stdin=PIPE, stdout=PIPE, stderr=STDOUT)
+        p = Popen(cmd, shell=False, bufsize=0, stdin=PIPE, stdout=PIPE, stderr=STDOUT)
     except OSError as e:
         return "nsupdate: execution failed: %s" % e
     except:
@@ -364,7 +364,12 @@ answer
     (output, err) = p.communicate(nsup.encode())
     if output.decode().find("status: NOERROR") >= 0:
         return None
-    return output.decode() + err.decode()
+    if not err is None:
+        ex = err.decode()
+    else:
+        ex = "noerr"
+
+    return output.decode() + ex
 
 
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